The incidence and prevalence of gastroenteropancreatic neuroendocrine tumours (NETs) has been increasing over the past three decades. Due to the high density of somatostatin receptors (SSTR), mainly SSTR2, on the cell surface of these tumours, [111In]-DTPA-octreotide scintigraphy (SRS) has become an important part of clinical management. More recently, however, [68Ga] labelled octreotate analogues are being increasingly used because of their improved sensitivity and specificity (Gabriel et al., 2007). Fluorine-18 radiolabelled analogues with suitable PK would permit positron emission tomography (PET) with more rapid clinical protocols. Previous work by this group, under a Developmental Pathway Funding Scheme (DPFS) award, designed five structurally-related [18F]-fluoroethyltriazole-[Tyr3]octreotate analogues. Based on high binding affinity and low tumour-to-background noise ratio, within this series and also compared to other related F-18 and Ga-68 SSTR imaging agents, we selected [18F]-FET-betaAG-TOCA as the lead compound to take forward into clinical development. We propose to develop [18F]-FET-betaAG-TOCA clinically via a 2 stage trial design. The initial study will assess the pharmacokinetics (PK), biodistribution and safety of the novel tracer employing 'whole body dynamic PET scanning'; of particular interest will be the optimal time for imaging. Using this information we will construct an appropriate protocol for 'whole body static PET scanning' in the subsequent study. We will then compare the diagnostic efficacy of [18F]-FET-betaAG-TOCA PET/CT to [68Ga]-DOTATATE PET/CT in patients with a histological diagnosis of NET. These clinical studies will be used as the basis for future larger clinical trials and a Department of Health application to establish this tracer as the new clinical standard based on equivalent sensitivity and specificity but improved kinetics and handling, as well as ease of GMP manufacturing than the existing [68Ga]-DOTATATE PET/CT.